tests/test-diffdir.t

template: fix shortest(node) function in pure mercurial

Pure mercurial (i.e. without c extensions) does not support partialmatch() on
the revlog index, so we must fall back to use revlog._partialmatch() to handle
that case for us. The tests caught this.

We don't use revlog._partialmatch() for the normal case because it performs a
very expensive index iteration when the string being tested fails to find a
unique result via index.partialmatch(). It does this in order to filter
out hidden revs in hopes of the string being unique amongst non-hidden revs.
For the shortest(node) case, we'd prefer performance over worrying about
hidden revs.

  $ hg init
  $ touch a
  $ hg add a
  $ hg ci -m "a"

  $ echo 123 > b
  $ hg add b
  $ hg diff --nodates
  diff -r 3903775176ed b
  --- /dev/null
  +++ b/b
  @@ -0,0 +1,1 @@
  +123

  $ hg diff --nodates -r tip
  diff -r 3903775176ed b
  --- /dev/null
  +++ b/b
  @@ -0,0 +1,1 @@
  +123

  $ echo foo > a
  $ hg diff --nodates
  diff -r 3903775176ed a
  --- a/a
  +++ b/a
  @@ -0,0 +1,1 @@
  +foo
  diff -r 3903775176ed b
  --- /dev/null
  +++ b/b
  @@ -0,0 +1,1 @@
  +123

  $ hg diff -r ""
  hg: parse error: empty query
  [255]
  $ hg diff -r tip -r ""
  hg: parse error: empty query
  [255]